I have encountered the same set of errors and logged a case with technical support after following the above advice(#03529617).

Details:

ADD 12.5 in Windows 10 was able to change the cluster size of the 100GB C:\ volume from 4KB to 8KB successfully. This required a reboot into the Acronis Boot environment to apply the change.

However I was unable to attempt a change of cluster drive on the Y:\ volume (4x4TB spanned dynamic volume).

Following up on this error, I completed a successful chkdsk /F /r which completed in 36 hours and found no errors.

This did not resolve the issue.

I then created a WinPE Bootdisk and attempted to conduct the same operation. I encountered the following additional errors:
Unable to create volume snapshot.
Block count limit of snapshot manager has been exceeded.

I then created a Linux bootable media and attempted to make the same change. Using this environment I am able to commit the change from 4Kb to 16Kb cluster size on the volume, and apply. But some time afterwards the system reboots into the OS with no changes having been made.